Need some help making a php search tree - php

Question

Im making a tree to store words and an associated number array in php. I need it to look something like this:
Words: apple, ant
[a] => Array
(
[p] => Array
(
[p] => Array
(
[l] => Array
(
[e] => Array
(
[0] => Array
(
[0] => 0
[1] => 0
[2] => 1
[3] => 2
[4] => 3
[5] => 4
)
)
)
)
)
[n] => Array
(
[t] => Array
(
[0] => Array
(
[0] => 0
[1] => 1
[2] => 2
[3] => 0
[4] => 0
[5] => 4
)
)
)
)
Of course apple and ant need to share the same [a] index. Im close, but I cant figure out how to properly keep track of the tree index so 'apple' gets into the tree fine but 'ant' is inserted as 'nt'. Heres my code at the moment:
private function insertWordsIntoTree()
{
foreach ($this->words as $word)
{
$characters = preg_replace('/[0-9]+/', '', $words);
$points = $this->getPoints($word);
$this->tree = $this->buildTree($characters, $points, $this->tree);
}
print_r($this->tree);
}
private function buildTree($characters, array $points, array $tree)
{
for ($i = 0; $i < strlen($characters); $i++)
{
$character = $characters[$i];
$remaining_characters = substr($characters, $i + 1);
if (strlen($characters) === 1)
{
$child = [];
$child[$character] = [$points];
return $child;
}
elseif (!isset($tree[$character]))
{
$tree[$character] = $this->buildTree($remaining_characters, $points, []);;
break;
}
else
{
$this->buildTree($remaining_characters, $points, $tree[$character]);
}
}
return $tree;
}
Im pretty sure the problem is at the else statement...I dont think Im keeping track of the current tree index properly. Any help would be much appreciated.

Answer 1

Here's a simple approach that passes the recursion off to php:
$tree = array();
foreach($words as $word) {
$characters = array_reverse(str_split($word));
$temp = array();
foreach($characters as $index => $character) {
if($index == 0) {
$temp[] = getPoints($word);
}
$temp = array(
$character => $temp
);
}
$tree = array_merge_recursive($tree, $temp);
}